The invention relates to the building of a radial tire with a special belt structure, using the flat-band method of building a tire, wherein the unvulcanized components of the tire are successively wrapped on a cylindrical tire building drum, to produce a generally cylindrical, unvulcanized tire which is then toroidally expanded within a rigid mold where the tire is molded and vulcanized. The use of such a method creates problems during the toroidal shaping of the tire, because of the normally low cord angle of the inextensible reinforcement cords of the belt structure and consequent restrictive action in limiting the circumferential expansion of the tire, which is necessary to the molding of the tire. For this reason, radial tires are usually toroidally shaped before the belt structure and remaining components are positioned on the tire. These problems are magnified when belt reinforcement cords of different materials, especially cords having widely divergent moduli of elasticity, or tensile strengths, are used. The invention is directed to solving such problems.
Briefly stated, the invention is in a radial tire and method of building the tire utilizing the flat-band process. The tire comprises the following components of fluid-impervious innerliner, at least one carcass ply with radially oriented reinforced cords surrounding the innerliner, a tread and pair of sidewalls surrounding the carcass plies and terminating at a pair of annular beads, and a belt structure. The belt structure comprises of at least one belt ply reinforced with textile cords having a low modulus of elasticity compared to the modulus of elasticity of the reinforcement cords of a belt ply which surrounds the textile cords. The surrounding belt ply or high modulus cords thereof is highly elongatable during the toroidal shaping of the tire. The surrounding belt ply after the tire has been molded and vulcanized does not contribute substantially to the restrictive effect of the belt structure.